The objective of the proposed research is to stuyd the steps in the enzymatic formation of conjugated bile acids in order to enhance understanding of the control of bile acid conjugation. Using methods developed in this laboratory, it is now possible to independently assay each of the enzymatic reactions necessary for conjugation. These assays will be used to study the subcellular distribution of the enzymes involved. The enzyme proteins involved in each reaction will be purified and the substrate affinities and substrate range will be studied for each step. Physiologic and pharmacologic controls of conjugation will be studied by assaying the individual reactions. Initial work will be performed in animal models as a prerequisite for future study in human tissue.